The specific aims of this project are: 1) to determine by indirect immuno fluorescent and by the avidin-biotin-peroxidase complex (ABC) immunoperoxidase techniques if mouse monoclonal antibodies developed against human melanoma antigens could localize tumor associated antigens (TAA) in cryostat and conventional paraffin sections of various histologic types of tumor; and 2) to determine by enzyme-linked immunosorbent assay (ELISA) if these monoclonal antibodies could detect TAS in cancer patients' sera. In recent months we have developed mouse monoclonal antibodies against TAA of the M14 CDM/COH cell line, a human malignant melanoma cell line which has been adapted to grow continuously in serum-free chemically defined medium (1). The specificity of monoclonal antibodies secreted by one hybridoma clone, as assessed by 125-I Staphy-lococcus Protein A (SPA) binding assay against a panel of various histologic types of tumor and normal fibroblast cell lines, suggested melanoma associated specificity. Two other hybridoma clones secrete monoclonal antibodies with apparent carcinoma associated specificity as determined by 125-I SPA binding assay against the above named panel of specificity as determine by 125-I SPA binding assay against the above named panel of specificity as determined by 125-I SPA binding assay against the above named panel of cell lines. The critical question regarding these monoclonal antibodies, pertinent to this project, is whether they could localize TAA in cryostat and routinely fixed paraffin-embeeded tissues of surgical tumor specimens. Our approach would be to determine by indirect immunofluorescence and by a sensitive ABC immunoperoxidase technique (2) the reactivity of these monoclonal antibodies against cryostat and conventional paraffin sections of normal and various histologic types of tumor tissues. Additionally, these studies propose to explore whether these monoclonal antibodies could be used in an ELISA for the quantitation of TAA in malignant melanoma and carcinoma patients' sera. While these studies emphasize diagnosis and prognosis of malignant disease information generated from these studies may open up the possibility of defining the TAA systems of human tumors and of elucidating the relationship between ocogenesis and ontogenesis.